The toxic effect of Co (II), Mn (II), and Zn (II) (as chloride salts) on growth of Raphidocelis subcapitata (formally named; Selenastrum capricornutum) was assessed through a standard algal growth inhibition test performed in accordance with ISO guideline 8692 (ISO, 2004). The results showed that the alga was more sensitive for high concentrations of Co (II) and Zn (II) metals. Statistical results of EC50 were 0.75% for Co (II) and 0.89% for Zn (II). Mn (II) found to be less toxic than the other tested heavy metals. High concentration of Mn induced several changes in cell and ultrastructure at cytoplasm, chloroplast and membrane levels in try to overcome the induced stress and detoxification of Mn.
Key words: Raphidocelis subcapitata, heavy metals, ultrastructure, toxicity bioassay, microalgae
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